The V8 Owners Forum -

Hi Guys,

I'm in the process of learning things regarding valve to piston clearance measurements when using hydraulic lifters.

As I understand one should measure the clearance by using a solid lifter and adjust for zero lash (when possible) or to using a solid lifter with your actual lifter pre-load correction.

Either way one should regard a clearance of approx .100" for the inlet valve. Some say an absolute minimum of .050" could be ok to.

This clearance is for: expanding components due to heat, valve bounce and pump up action when revving the engine to high.

I hope I'm correct up to now.

But the following thing is bothering me because I don't understand this. How does a lifter looks like in a pumped up state due to high revving on the end of the opening movement of the inlet valve (maximum lift)?

This in three situations:
1- Standard lifter
2- High revving lifter
3- Roads Bleed down lifter

In case of lifter C one should take into account a additional clearance of not 1.6 (rocker ration) times the pre-load but als times the pre-load with .030" for the small plunger in the middle.

I made a drawing to explain things.

Many thanks for your help

Frank

Play safe and use a solid lifter to check piston to valve clearances as a worst case scenario. Once you know the clearances you can install the lifters with safety. There's no lash as such because you preload the lifter. Manufacturers usually specify the amount of preload required. It could be .040" - .004" depending on the brand and engine type. If you don't have some preload you'll get a rattling valvetrain. You need more clearance for the exhaust valve as it's opening when Mr piston is coming to say hello

It's a bit tricky to get just one solid lifter. So I've to make my own but I don't know in what state (A, B or C) I should glue the lifter.

Kind regards

Frank

The solid lifter should have the same dimension as a normal lifter when it is not under load. So if you have a lifter in your hand it does not matter if it is dry or full of oil. The cup plate on top should be up against the circlip that holds it in. This simulates the lifter fully pumped up. And this is how you should check for piston clearance.
If I understand your diagram properly it would be C.

If the hydraulic lifter is not under load it will look like lifter 'B'. This smallest cup has no spring behind it and only the oil pressure could push it up but I was under the impression that the maximum oil pressure won't be enough to win it from the spring pressure when the valve are open.

My understanding was that during pump up state it's the one way valve (not showing in my drawings) at the bottom of the middle plunger that can't keep up. Therefore the pressure in the bottom chamber will be always equal or higher than the upper chamber. Thus the middle plunger will push itself onto the retainer.

But I'm not sure, of coarse.

Kind regards,

Frank

If the hydraulic lifter is not under load it will look like lifter 'B'.

If the lifter is not under any load it will look like lifter C.

I am talking about the lifter not having a push rod fitted. Empty or full of oil the lifter cup plate will be pushed up against the circlip. This is the maximum lift that can be gained and is the point at which you should measure piston to valve clearance for maximum safety.

I may be mistaken but the ones I have here laying around it's the middle plunger that is touching the circlip not the smallest (top) one. The smallest plunger that touches the pushrod is loose. You can here them rattling around when I shake the lifter. I measure an approx clearance of 0.8mm with the circlip from this smallest plunger. I always presumed one should measure the preload clearance underneath the circlip and the rim of the middle plunger. At least I think I saw that in a picture on the website of RPi Engineering. The v8wizards

I have the feeling I'm missing something. I'll try to make some photographs this evening and take one apart.

Kind regards,

Frank

Frank.de.Kleuver wrote:I may be mistaken but the ones I have here laying around it's the middle plunger that is touching the circlip not the smallest (top) one. The smallest plunger that touches the pushrod is loose. You can here them rattling around when I shake the lifter. I measure an approx clearance of 0.8mm with the circlip from this smallest plunger. I always presumed one should measure the preload clearance underneath the circlip and the rim of the middle plunger. At least I think I saw that in a picture on the website of RPi Engineering. The v8wizards

I have the feeling I'm missing something. I'll try to make some photographs this evening and take one apart.

Kind regards,

Frank

Hi Frank,
I have examined 2 different makes of new unused RV8 lifters and the centre part that pushes on the pushrod is hard against the circlip and doesn't rattle. It is the full size of the lifter internal bore and i cant see the other plunger you have mentioned.

Regards Denis

I may be on to something. I've made a photograph of my old standard Rover lifter and the new Rhoads lifter I tend to install.


But if I look at the drawing of the Rover manual you can see the smallest plunger is as wide as the lifter inner bore. So this would hit the circlip and no inner (small) plunger would be visible.



Kind regards,

Frank

OK!!
I'm with you now.

If you are fitting the Rhoades lifters you will still measure pre load between the bottom of the circlip and the top of the middle plunger.

I have fitted lots of Rhodes lifters and they dont rattle when empty?